1. Field of the Invention
This invention relates to a truck for use with railroad cars and particularly to a truck which allows relative yawing movement between a wheelset of the truck and side frames of the truck as the railroad car proceeds, for example, around a curve in a section of track on which the railroad car is traveling.
2. Prior Art
Today most all railroad car trucks in use include spaced side frames resiliently supporting therebetween a transversely positioned bolster. The bolster contains a centerplate which in turn supports a body of the railroad car. The side frames have downward projecting jaws in which axle ends of a front and rear wheelset are rotatively journaled. Such trucks may be referred to as nonsteerable trucks.
Steerable trucks are ones having wheelsets which may yaw. Such trucks are well known and one typical type is disclosed in U.S. Pat. No. 3,789,770. As disclosed, this truck allows rotation of each wheelset about its vertical axis so that the wheelset may take an out-of-square position with respect to a longitudinal axis of the truck. The wheelsets are joined by positive mechanical linkage which controls and maintains the relationship between the wheelsets. Additionally, this linkage is connected to a body of the railroad car so that movement between the car body and the wheelsets is maintained in a fixed relationship.
Providing a flexible connection between the axle ends of the wheelset and the side frame to allow yawing therebetween is also well known and is disclosed in, for example, U.S. Pat. No. 3,785,298. In this case, a resilient or elastomeric device interfaces between pedestal jaws of a side frame of the truck and axle ends of the wheelsets to allow limited movement therebetween which is restrained by the elastomeric device.
U.S. Pat. No. 3,528,374 discloses a truck which is perhaps the first to adapt the steering principle to a modern day truck. In this instance, a bolster has its ends resiliently carried by side frames. Ends of the side frames are adapted to allow the wheelsets of the truck to yaw. Yawing in turn is regulated by parallel elastic bracing members connecting aligned front and rear axle ends and diagonally positioned elastic bracing members connecting opposite front and rear axle ends.
A further arrangement to provide a truck with wheelsets which can yaw so as to maintain an aligned relationship with the track on which the truck is traveling is disclosed by U.S. Pat. No. 4,003,316. As so disclosed, holding frames which carry the axle ends of the wheelsets are individually connected to a bolster of the truck through a ball bearing socket arrangement enclosed in a pad. Any lateral movement of the bolster effects a rotational movement of the holding frame and thus the wheelsets.
Most recent development in steerable trucks is perhaps disclosed in U.S. Pat. Nos. 4,067,261 and 4,131,069. The disclosure of the first patent places particular emphasis on the use of wheels having highly profiled wheel treads to generate steering forces. A pair of U-shaped subframes carries the axle ends of each wheelset and may be interconnected by a pair of diagonally positioned rods. These rods may be interconnected through a dampening means.
The U.S. Pat. No. 4,131,069 discloses a further steerable railroad car truck wherein resilient means of predetermined stiffness interconnects the axle ends carrying subframes of the truck at a centrally located point. Additionally, resilient means interconnect the subframes with the side frames of the truck and the truck with a body of the car.